Surface waters that do not percolate into the ground may flow over a variety of substrates (e.g., paved or unpaved streets or lots, fertilized or mined land, and construction sites) and in so-doing accumulate substances (e.g., chemicals, debris, particulates, sediment, silt, and pollutants) that can adversely affect water quality of watershed systems into which they flow. The detrimental effects of unclean and/or contaminated surface water runoff are vast and well known; and have led to the creation of the Clean Water Act by the Federal Government and significant enforcement thereof by the Environmental Protection Agency (EPA). The EPA's National Pollutant Discharge Elimination System (NPDES) is authorized by the Clean Water Act and typically requires municipalities to implement controls and best management practices (BMPs) that reduce pollutants in surface water flows or discharges from municipal facilities, e.g., as identified in a storm water management plan prepared in accordance with 40 CFR Part 122.44(k)(2). NPDES also imposes standards regarding the content of sediments, nutrients, metals, organics, bacteria, and oils in surface waters that flow into storm or sewer drains.
One approach for improving surface water quality prior to its entry into natural watersheds through storm or sewer drains is filtration. A previous filtering device for use in storm or sewer drains is described in U.S. Pat. No. 7,186,333, by Kluge, the content of which is hereby incorporated by reference in its entirety.